Why does Les spend so much time on Paul's epistles?
Because the Pauline epistles are where Gentiles in the Grace Age find the meat of their faith and practice, and Paul is the Apostle of the Gentiles. Scripture's other portions are not discarded, but priorities are set, and Paul's writings hold priority for the believer.
Les teaches that this is why he spends so much time on Paul's epistles: Ephesians 3 shows that this is where Gentiles have to spend their greatest amount of time. He stresses that this does not cancel the rest of Scripture, and he denies telling people to throw away the four Gospels. Never do we take away any portion of Scripture, but we have to set priorities. The priority for the Grace Age Gentile believer, and for the Jew who has come into Christianity as a born-again person, is that these Pauline epistles are where we find the very meat of our faith and practice. Romans 11:13 also establishes Paul as the Apostle of the Gentiles.